Atletico Madrid president Enrique Cerezo says Thibaut Courtois could still miss the Champions League semi-final tie against Chelsea.
The Belgium international seemed destined to sit out the clash with his parent club due to a clause in his loan deal stating that Atletico would have to pay Chelsea up to €6 million (£4.9m) if they were paired together.
However, Uefa ruled last week that such an agreement was invalid in European competition, but Cerezo remains cautious over Courtois' participation.
"I think he’ll end up playing against Chelsea, but only if we reach an agreement with them," Cerezo told reporters.
"We’re gentlemen and we observe everything we sign.
"Courtois is Chelsea’s player and we’re trying to get him on loan for another season.
"I don’t think there will be consequences from Uefa. I think he’ll play, but only with an agreement between both parties.
"If he doesn’t play, [Daniel] Aranzubia will come in."
Courtois has been a key figure for Atletico so far this season, making 47 appearances in all competitions.